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    Pool Shock Guide

    Pool Shock is the casual term for granular oxidizer, used to remove contaminants and particles from the pool water. It is also one of the most volatile pool chemicals, and must be clean, closed, dry and separated from other pool chemicals.

    More on pool shock safety later, for now lets discuss the questions of what, when, and how much pool shock to use.

    What: Types of Pool Shock

    Calcium Hypochlorite: Cal Hypo pool shock is the most common and most economical type of pool shock, sold in 1 lb. bags and in 25 lb. or 50 lb. buckets. The high pH level of 12 may raise pool pH level with heavy use. 65% Available Chlorine, per pound or 73% available with our Super Pool Shock - 21 oz. adds 10 ppm FC, per 10,000 gallons of pool water.

    Dichloro-S-Triazinetrione: Dichlor pool shock is the only stabilized form of granular pool shock, made with cyanuric acid to protect it from the sun, and is sold in 1 lb. bags and in 25 lb. or 50 lb. buckets. A neutral pH level of near 7.0 may lower pool pH level with heavy use. 56% Available Chlorine - 25 oz. adds 10 ppm FC, per 10,000 gallons of pool water.

    Lithium Hypochlorite: Lithium pool shock is a close cousin of Cal Hypo, but contains no calcium, and is a quick dissolving very fine granular, allowing you to swim immediately. A perfect pH level of 7.4 will not alter pool pH levels. 35% Available Chlorine - 38 oz. adds 10 ppm FC, per 10,000 gallons of pool water.

    Potassium Monopersulfate: Non-Chlorine Shock MPS contains no chlorine, and no calcium or cyanuric acid. Quick dissolve granular shock powder is safe for all surfaces, has no pH effect, and you can swim immediately. MPS is less effective on algae and bacteria, but removes chloramines, ammonia, bather waste and other organic contaminants.

    When: Should You Shock a Pool

    There are really 3 main reasons to shock a pool or spa, raising the Free Chlorine level high enough (10-30 ppm) to oxidize or destroy the offending contaminants. These could be called the A-B-Cs of Pool Shock.

    Algae: Green, yellow, pink or black, the best algaecide is chlorine, and lots of it. Be sure that the pH is adjusted to 7.1-7.3 range, so the chlorine shock is most potent. Depending on the severity of the algae, 10-30 ppm is needed to kill active algae blooms.

    Bacteria & Bather Waste: Bacteria can enter the pool from many sources, most of it harmless variety, however pathogenic bacteria may also exist. Use chlorine shock to remove bacteria after heavy pool use, heavy storms, long winters or for swimmer "accidents." Bather waste includes skin, hair, lotions, cosmetics and soaps, as well as sweat, urine, feces and fungus.

    Chloramines, Contaminants, Cloudy Water: Combined chlorine molecules are responsible for red-eye and a strong chlorine smell. When Chloramine levels exceed 0.5 ppm (TC-FC=CC), add enough chlorine or non-chlorine shock to break apart the combined chlorine, usually 10-20x the tested CC level.

    Shocking the pool also removes organic contaminants from dirt, leaves and air pollution. There is a lot of harmless matter that gets into a pool and gets in the way of water balance and sanitation. Cloudy water can often be corrected by superchlorinating the pool, or by adding non-chlorine oxidizer, to destroy the colloidal particles that cause cloudy water.

    In short, for best results, use Chlorine Shock for Algae and Bacteria removal, and use Non-Chlorine Shock for Chloramine and Contaminant removal and treatment of Cloudy Water.

    How Much: Pool Shock to Use

    How much pool shock to do the job depends on what job you giving it. Severe algae or bacterial contamination takes as much as 30 ppm (4 lbs of Cal Hypo per 10,000 gals), while general disinfection or chloramine removal can often be accomplished with 5-10 ppm (1 lb. of Cal Hypo per 10,000 gals).

    In most cases, follow the dosage treatment guidelines printed on the bag or bucket of pool shock. This will be sufficient to kill most bacteria and developing algae colonies, and destroy contaminants and chloramines.

    Algae: For severe algae (green pool), and other out of control water issues, a 2-6x normal dose is used to oxidize all of the suspended material, organic matter and bacteria in the water. 10-30 ppm is a good target, see dosage for each shock type listed above.

    Bacteria & Bather Waste: For most common bacteria and bather waste, a level of 10-20 ppm will oxidize most contaminants, see dosage for each shock type listed above.

    Chloramines & Contaminants: To break apart chloramine molecules, shock to a level that is 10x the tested level of combined chlorine (using a DPD test kit). For general organic contaminant removal, including water clouding colloidal particles, 10 ppm is generally sufficient. Chlorine free shock can also be used for all such cases as a clean alternative.

    If you use Cyanuric Acid or Stabilizer in the pool, you should increase the ppm target by 10%, for each 10 ppm of cyanuric acid in the water, as cyanuric acid will suppress the chlorine activity.

    Similarly, if pool pH is above 7.8, half of the efficacy or power of Free Chlorine is lost, and above pH 8.4, almost all is inactive or slow to react. Always lower pH before shocking to 7.1-7.3, for best results.

    For pools in hard water areas that don't want to add calcium to the water (Cal Hypo), or don't want to add cyanuric acid to the water (DiChlor), you can use Non-Chlorine Shock to remove contaminants, chloramines and clear cloudy water. Non-chlorine shock is not a great disinfectant however, so when shocking the pool for Bacteria or Algae removal, the power of chlorine is recommended. Lithium Hypochlorite contains no stabilizer or calcium but is nearly twice the price of Cal Hypo or DiChlor shock.

    Pool Shock Safety

    Storing Pool Shock: Keep in a cool, dry area, separated from other pool chemicals, and out of reach of children. Shock is more safely stored if removed from the cardboard box and placed inside a clean bucket or storage bin with a tight fitting lid. Do not store half-used bags of shock, which could spill, become contaminated, or take on moisture.

    Using Pool Shock: Cut bag carefully with scissors, and pour into the water while walking along the pool edge. Use a pool brush to distribute, and sweep or wash any spills into the pool. Vinyl liner pools should pre-dissolve granular shock, unless using quick dissolving Oxy Shock or lithium pool shock.

    Never Mix Pool Shock: With anything except Water. Pool shock is very reactive and when mixed with any substance other than water, it can release toxic gases, ignite or explode. Never place shock into a chlorinator or floater, or add to the skimmer, always add directly to the pool.